
sp = input().split()
st = ''
for el in sp:
    if el == 'zero':
        st+= '0'
    elif el == 'one':
        st+= '1'
    elif el == 'two':
        st+= '2'
    elif el == 'three':
        st+= '3'
    elif el == 'four':
        st+= '4'
    elif el == 'five':
        st+= '5'
    elif el == 'six':
        st+= '6'
    elif el == 'seven':
        st+= '7'
    elif el == 'eight':
        st+= '8'
    elif el == 'nine':
        st+= '9'
    else:
        print('Wrong input')
        break
if len(st) == 3:
    n = int(st)
    num = 0
    flag = True
    while flag:
        nmin = n-num
        nmax = n+num
        for i in range(2, nmin//2+nmin%2+1):
            if nmin % i == 0:
                break
            if i == nmin // 2 + nmin%2:
                print(nmin)
                flag = False
        for i in range(2, nmax//2+ nmax%2+1):
            if nmax%i ==0:
                break
            if i==nmax//2 + nmax%2:
                if flag:
                    print(nmax)
                    flag=False
        num+=1
    
    
    
    
    